The present disclosure relates to magnetic toners for developing an electrostatic latent image.
For energy saving and downsizing of an image forming apparatus, there is a demand for a toner excellent in low-temperature fixability. If a toner excellent in the low-temperature fixability is used, a toner can be satisfactorily fixed on a recording medium even if the temperature of a fixing roller is low.
In order to obtain a toner excellent in the low-temperature fixability, a method for producing a toner by using a binder resin having a low melting point (or a binder resin having a low glass transition point) and a mold releasing agent having a low melting point has been proposed. It is, however, difficult to produce a toner excellent in high-temperature preservability by this method. The high-temperature preservability of a toner refers to a property that toner particles contained in the toner are not aggregated even if the toner is stored under a high-temperature environment. In a toner poor in the high-temperature preservability, toner particles are liable to aggregate under a high-temperature environment. When the toner particles aggregate, the charge amount of the toner particles are likely to be lowered.
For purpose of improving the low-temperature fixability, high-temperature preservability, and blocking resistance of a toner, a toner containing toner particles having a core-shell structure has been proposed.
In an exemplified toner containing toner particles having a core-shell structure, a toner core contains a binder resin having a low melting point. Besides, the toner core is coated with a shell layer made of a resin. In addition, the resin constituting the shell layer has a higher glass transition point (Tg) than the binder resin contained in the toner core.
In another exemplified toner containing toner particles having a core-shell structure, the surface of a toner core is coated with a thin film (shell layer) containing a thermosetting resin. The toner core has a softening point of 40° C. or more and 150° C. or less.